The spatial distribution of turloughs

Abstract

Preliminary observations are made on the distribution of turloughs (seasonal lakes) on the Irish Carboniferous Limestone. The majority of turloughs are located on well-bedded, pure, grey calcarenite, lithologically similar to the Burren Limestone. In contrast, turloughs are not found on impure, shaly Calp limestone, or on the massive Waulsortian bank limestone. The purity and well-developed bedding of the Burren-type limestone may render it particularly susceptible to karstification, favouring the development of turloughs. Structural geology is not thought to play an important role in the siting and orientation of turloughs.

Turloughs tend to occur in glacial depositional landscapes with gently undulating relief. The area surrounding a turlough is usually soil-covered, but limited evidence suggests that the glacial drift is relatively thin and permeable. Thus the absence of turloughs from some areas of suitable bedrock is thought to be due to thick glacial drift (e.g. east of Portlaoise), or impermeable drift (e.g. in the northern drumlin belt).